Application of a multicoloring technique making use of a color conversion method to liquid crystal displays, organic electroluminescent (EL) displays, lighting devices, and other devices is being energetically studied. Color conversion means conversion of light emitted from a light-emitting body into light having a longer wavelength, and, for example, indicates conversion of blue light emission into green or red light emission.
A composition having such a color conversion function (hereinafter, referred to as a color conversion composition) is used, and combined with, for example, a blue light source, whereby the three primary colors, namely, blue, green, and red can be extracted, in other words, white light can be obtained from the blue light source. A white light source obtained by combining the blue light source with the composition having the color conversion function is used as a backlight unit, and a combination of a liquid crystal driving unit and color filters allows a full-color display to be produced. Without the liquid crystal driving unit, the residual part can be used as a white light source as it is, which can be applied as a white light source such as light-emitting diode (LED) lighting using an LED.
Examples of a problem with a liquid crystal display making use of a color conversion system include the enhancement of color reproducibility. To enhance color reproducibility, making a full width at half maximum of each of blue, green and red emission spectra of a backlight unit narrower and thereby enhancing the color purity of each of blue, green and red are effective.
To solve this problem, there has been proposed a technique of using a combination of a light emitting body having a light emission peak wavelength in a wavelength range of 240 nm to 560 nm, a green phosphor having a light emission peak wavelength in a wavelength range of 510 nm to 550 nm, a red phosphor activated by a tetravalent manganese ion, and a color filter having a blue pixel in which the difference between the maximum and the minimum of a transmittance in a wavelength range of 420 nm to 460 nm in a spectral transmittance curve is 4% or smaller (for example, see Patent Literature 1).